Studies of the electronic structure at the Fe3O4–NiO interface

Abstract

The interfacial electronic structure between the metallic ferrimagnet Fe3O4 and the insulating antiferromagnet NiO is investigated in the lattice matched heteroepitaxial system Fe3O4 (100)–NiO (100) by growing ultrathin NiO films on single-crystal Fe3O4 (100) substrates. The Fe3O4 (√2×√2)R45° surface is characterized prior to growth by low-energy electron diffraction, reflection high-energy diffraction, scanning tunneling microscopy, ultraviolet photoelectron spectroscopy (UPS), x-ray photoemission spectroscopy (XPS) and Auger electron spectroscopy. UPS and XPS, which sample several monolayers in the substrate–overlayer structure, are used to monitor near-surface electronic properties versus NiO overlayer thickness. Comparison of experimental He II UPS spectra of the valence band electronic structure with a simple model of substrate–overlayer emission indicates that the electronic transition from Fe3O4 to NiO is nearly atomically sharp.